1. Field of the Invention
The invention relates to devices converting a particle non-confining wave into a particle confining wave, the non-confining wave being emitted by a laser in the far infra-red, more particularly by a carbon dioxide laser.
2. Description of the Prior Art
Devices of the aforementioned kind generating confining waves, more particularly circular-polarized waves having a phase shift proportional to the azimuth are known inter alia from U.S. application Ser. No. 863,235 filed by the present Applicant on Dec. 22, 1977. The known devices comprise a laser proper, emitting a non-confining wave, a quarter-wave plate and a mode converter for converting the non-confining wave into a confining wave. The aforementioned patent application described two kinds of mode converter. The first kind uses an isotropic material transparent to the laser wave and in the form of a helix or spiral staircase, the pitch of the helix or the height of the steps being suitably determined. The other kind of mode converter uses a material which is birefringent at the laser frequency and is cut into sectoral segments which are fitted together to form circular discs, the slow and fast axes of the birefringent material in each sector having a predetermined orientation relative to the bisector of the sector. Since no known material is birefringent in the far infra-red, quarter-wave plates of birefringent material and mode converters of the second kind, which are also of birefringent material, cannot be used in the far infra-red. On the other hand, some existing isotropic materials are transparent to waves at a wavelength of 10 .mu.m.
The object of the invention is to provide a device generating a confining wave at a wavelength near 10 .mu.m, wherein the device converting a rectilinear polarized wave into a circular polarized wave is made of isotropic material transparent to the laser wave.